Russia and Turkey’s defense ministers on Monday agreed on taking what they called decisive measures to stabilise the situation in Syria’s Idlib province, Russia’s RIA news agency reported.

The agreement between Hulusi Akar and Sergey Shoygu in Ankara follows a Turkey-brokered deal in September to create a demilitarised zone in the northwest Idlib region to be cleared of all heavy weapons and radical fighters.

Turkey, a major backer of Syrian rebels, and Russia, the main ally of Syrian President Bashar al-Assad’s regime, signed the agreement on rebel-held Idlib as Assad regime forces were about to launch an attack on the western Syrian province.

Ankara spoke of “the need in particular to take decisive measures to ensure security in the Idlib demilitarised zone,” RIA reported, citing a joint statement published after the talks between the two defense ministers.

The United States, which lead the war against ISIS in the region, announced its withdrawal from the northern Syria in December amid ongoing concerns by NATO ally Turkey of the threat caused by US-backed Kurdish militants in the region.